In subterranean engineering, i.e. the construction of tunnels, galleries or shafts, it is frequently desirable to stabilize the excavated structure by anchoring wall or support members thereto and, for this purpose, drilling and bolting machines have been developed as, for example, will be apparent from the aforementioned applications and patents.
The procedure which can be carried out with the aid of such machines involves the drilling of a so-called borehole and the subsequent anchoring of a bolt therein. Frequently the anchoring of the bolt can be effected at least in part by introducing into the hole in which the bolt is inserted, a hardenable synthetic resin mass, especially a thermosetting synthetic resin.
The drilling and bolting turret can have a girder mounted to pivot about a pivot pin at the end of a support arm and comprising means for guiding the sliding of two carriages in a direction parallel to the pivoting axis of the girder, one carriage being for drilling a hole and the other for the introduction of a bolt into the hole drilled and for its tightening, as well as means for controlling the advance and withdrawal movements of the two carriages, means such as a jack being provided for controlling the pivoting of the girder in order to bring the second carriage into line with the axis of the hole drilled previously by the first carriage, whereas other means such as a jack are provided for moving the arrangement of the girder longitudinally parallel to its pivot axis.
A turret of this type, which is used in the field of mining, in particular for the work of supporting the "roof" and the "faces" of a mine-level, is already described for example by French Pat. No. 1 359 297. This turret is equipped to drill a hole by means of the first carriage which drives a drilling bit and then in order to introduce a bolt into the hole and tighten it by means of the second carriage, constituting a screwing device. Anchoring of the apparatus to the "roof" or "face" of the level is carried out along the pivoting axis of the turret, in order that before it is fitted, the axis of the bolt corresponds exactly to the axis of the hole drilled. A turret of this type is advantageously associated with a bolt magazine, in order to be able to drill a series of holes and introduce bolts into the latter virtually without manual intervention.
In the construction known from French Pat. No. 1 359 297, the girder is integral with two bearings mounted to slide on a tube, which is mounted to pivot at the end of the support arm. The jack controlling pivoting is hinged at a wrist-pin integral with the tube and a rotary connection by cotter-pins allows the girder to rotate at the same time as the tube, whilst allowing sliding of the girder parallel to its pivot axis. The anchoring along this pivot axis is achieved by a point integral with the tube and the jack for so called full retraction or advance which controls the sliding of the girder along this tube forms an integral part of the structure. This entire arrangement has various drawbacks:
(a) owing to the rotation of the tube, the wear is considerable and the positioning lacks precision. PA1 (b) the presence of cotter-pins prevents the use of gaskets. PA1 (c) the pivoting of the anchoring point, with the turret arrangement, brings about crumbling of the "roof" or of the "face", thus resulting in poor anchorage. PA1 (d) the travel of the jack for full retraction or advance is limited. PA1 (a) Reduction of wear and more precise positioning, PA1 (b) Owing to the elimination of the cotter pins, the possibility of using gaskets and the possibility of scraping. PA1 (c) Anchorage by a point which does not pivot with the girder, since it is supported by a fixed member, thus giving rise to more effective anchoring. PA1 (d) Control of the longitudinal movement of the girder by an independent jack, with greater travel.
Furthermore, in the known turret construction to which reference is made, the girder has an "H" section and the means for guiding the two carriages are constituted by the two parallel flanges of this girder. The guide surfaces are relatively weak and cannot be replaced in the case of wear. In addition, this arrangement reduces visibility from the operator's working position.